Gas dynamic cold spray unit

ABSTRACT

A gas dynamic spray unit is provided that includes gun housing halves secured about a heater assembly. The heater assembly is retained within the gun housing using locating features provided on the heater assembly and the gun housing. An outlet fitting is secured to the heater assembly and supports a nozzle having a venturi that accelerates a carrier gas. The carrier gas is supplied to the nozzle by a passageway. A powder feed passage communicates with the nozzle to provide powdered material to the accelerated carrier gas, which is expelled from a tube. The passageway includes an aperture for leaking carrier gas inside the gun housing to pressurize the gun housing and prevent powdered material from infiltrating the gun housing. A shroud is secured to the gun housing about the tube to prevent damage to the tube and protect the user from contacting the hot nozzle and tube. Data supplied from the esp@cenet database—Worldwide

BACKGROUND

This application relates to a gas dynamic spray unit. More particularly,the application relates to a gas dynamic spray gun and heater core foruse therewith.

Portable gas dynamic spray guns are being developed to widen theirapplication and reduce the cost of using cold spray technology.Low-pressure cold spray systems are used for spraying powdered materialat supersonic velocities. The low-pressure carrier gas is supplied tothe spray gun at typically less than 10 bar (150 psi). The carrier gaspasses through a heater assembly, which heats the carrier gas to reduceits density. The heated gas then flows through a venturi throat and isaccelerated. Powdered material is then introduced into the gas jet andis expelled at a supersonic velocity towards a substrate. The powderedmaterial typically includes a single constituent abrasive, metal, metalalloy or a blend of such materials. The powdered material can be used toprepare (clean or abrade) the surface or deposit a coating onto thesubstrate.

It is desirable to commercialize portable gas dynamic spray units, whichhas not been done very successfully. Prior art cold spray guns arerather heavy and can pose safety issues to the user due to the highoperating temperature of the heater assembly, which may be between400-650° C. during use. Moreover, packaging the cold spray guncomponents in a portable size that is also durable can be difficult. Forexample, the heater assembly in some cold spray guns is susceptible tobreakage and electrical shorts due to rough handling. Other heaterassemblies, which are rather heavy and not adapted to cold spraytechnology, generate heat in such a way that would expose the user tovery high temperatures.

What is needed is a gas dynamic spray unit more suitable forcommercialization.

SUMMARY

A gas dynamic spray unit is provided that includes gun housing halves,which may be a polymer, secured about a heater assembly. The heaterassembly includes a one-piece, multi-passage ceramic heater core. Theheater assembly is retained within the gun housing using locatingfeatures provided on the heater assembly and the gun housing.

The heater assembly includes a heater housing at least partiallysurrounding the heater core. A biasing member biases the ceramic heatercore toward a tapered outlet, which is provided by a deflecting conesurrounded by an insulating cone.

An outlet fitting is secured to the heater assembly and supports anozzle having a venturi that accelerates a carrier gas. The carrier gasis supplied to the nozzle by a passageway. A powder feed passagecommunicates with the nozzle to provide powdered material to theaccelerated carrier gas, which is expelled from a tube. The passagewayincludes an aperture for leaking carrier gas inside the gun housing topressurize the gun housing and prevent powdered material frominfiltrating the gun housing. A shroud is secured to the gun housingabout the tube to prevent damage to the tube and protect the user fromcontacting the hot nozzle and tube.

These and other features can be best understood from the followingspecification and drawings, the following of which is a briefdescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an example cold spray unit.

FIG. 2 is a partially broken cross-sectional view of an example spraygun, which is illustrated in FIG. 1.

FIG. 3 a is a cross-sectional view of a heater assembly taken along line3 a-3 a in FIG. 3 b.

FIG. 3 b is a side elevational view of the heater assembly shown in FIG.3 a.

FIG. 3 c is an end view of the heater assembly shown in FIGS. 3 a and 3b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A cold spray unit 10 is shown in FIG. 1. The unit 10 includes a controlunit 18 connected to a power supply and a gas source 14 via a gas supply16. A spray gun 20 is connected to the control unit 18 by a servicecable 22. The control unit 18 controls and monitors the various inputsand outputs of the unit 10 to obtain desired deposition of powdermaterial onto the substrate. For example, the control unit 18 monitorsand regulates the process parameters such as gas pressure, gas flowrate, heater temperature, and powder system sequencing. The control unit18 allows the operator to monitor and adjust settings and provide dataon maintenance status, process efficiency, and communicate this data toa higher order control.

A powder feeder 24 having one or more powder containers 26 suppliespowder material to the spray gun 20 for deposition onto a substrate. Thepowder feeder 24 supplies a regulated amount of powder to the spray gun20. Example powdered materials include ceramic, metal, metal alloy, orother hard materials. The powdered material is supplied to the spray gun20 at the times and rates commanded by the control unit 18. It isdesirable for the powder containers 26 to be designed to withstand somepressure, which may be caused by an obstruction downstream during thespraying process.

The spray gun 20 is shown in more detail in FIG. 2. The spray gun 20includes a gun housing 28, which is two plastic halves secured to oneanother in one example. In one example, the gun housing 28 isconstructed from an impact and heat resistant glass-reinforced polymer.Providing two halves simplifies assembly.

The service cable 22 is secured to a handle 29 of the spray gun 20 by astrain relief fitting 31. The service cable 22 includes adequateprotection for the internal connections and passageways that it houses.A trigger 33 is provided on a handle 29 and signals the control unit 18to turn on or off. The control unit 18 directs the flow of carrier gasand, with appropriate feedback signals, allows feeding of powders andperforms regulation of the powder-laden gas jet. An indicator on the gunhousing 28 (not shown) provides confirmation to the operator of theselected operating mode.

A heater assembly 34 is arranged within the gun housing 28 to rapidlyheat the carrier gas and reduce its density. The heater assembly 34includes an inlet fitting 36 that receives a gas inlet 30 secured to agas line 32. The gas line 32 provides a carrier gas to the spray gun 20.Features provided by the gun housing 28 are used to locate the heaterassembly without requiring additional fasteners. In one example, theinlet fitting 36 includes an annular groove 38 that receives aprotrusion 40 provided by the gun housing 28 to locate the rear portionof the heater assembly 34 within the spray gun 20.

In one example, the inlet fitting 36 includes an aperture 99 thataccommodates a heating wire for a heater core 42 (FIG. 3). The aperture99 is in communication with a passageway the supplies the carrier gas tothe heater core 42. The aperture 99 is designed to create a controlledleak within the gun housing 28 that pressurizes the spray gun 20, whichprevents infiltration of the powdered material into the gun housing 28.The leaked carrier gas escaped between the gun housing joint halves aswell as other areas of the spray gun 20 (such as the front, which ishottest).

Referring to FIG. 3 a, the heater assembly 34 provides the heater core42 that receives the carrier gas from the gas line 32 and heats it to adesired temperature, typically between 400-650° C. In the example, theheater core 42 is a one-piece ceramic structure that is relativelysimple to manufacture. The ceramic heater core 42 better ensures thatthe gun housing 28 does not become too hot for an operator to handle.The heater core 42 is a multi-passage arrangement. In the example, theheater core 42 includes an outer wall 50 concentrically arranged aboutfirst and second spaced apart walls 52, 54. An inner wall 56 is arrangedwithin the second wall 54. The walls 50, 52, 54, 56 respectively providean outer passage 58 and first and second passages 60, 62.

In one example, support legs 55 extend radially between the inner walland first wall 56, 52, as shown in FIG. 3 c. Similar support legs (notshown) extend between the first and second wall 52, 54 and second andouter wall 54, 50. In this manner, a one-piece ceramic structure can beprovided. In one example, the support legs 55 are continuous the lengthof the flow passages, which are divided the support legs 55 intocircumferentially arranged flow channels 57, best shown in FIG. 3C.

A heater housing 44, which is stainless steel in one example, surroundsthe heater core 42. In one example, the heater housing is spin formed toreduce its weight and thermal mass. An end of the heater core 42 isreceived in a retaining cup 46, which is biased forward by a biasingmember 48 (for example, a spring) arranged between the retaining cup 46and the inlet fitting 36. The biasing member 48 accommodates thermalexpansion of the heater assembly components without overstressing any ofits fragile components, such as the ceramic heater core 42. Moreover,the biasing spring 48 reduces issues relating to tolerance stack-upswithin the heater assembly 34. An end of the heating core 42 oppositethe retaining cup 46 extends axially outward relative to the outer wall50 and is received in an aperture 69 of an insulating cone 68. Theinsulating cone 68 keeps the temperatures at the front of the gunhousing 28 to a minimum and reduces any shock transmitted to the ceramicheater core 42.

Heating elements 64 are arranged within the first and second passages60, 62 in the example shown. Additional and/or fewer heating elementscan be used depending upon the amount of heat desired and the packagingconstraints. In operation, the carrier gas flows into the heater housing44 through the inlet fitting 36 via the gas inlet 30 (FIG. 2). Thecarrier gas flows along the inner surface of the heater housing 44radially outward of the heater core 42. This first pass of carrier gasalso acts to insulate the heated gases at the interior of the heatercore 42 and minimize heat transfer to the gun housing 28. The carriergas flows through the outer passage 58 and simultaneously through thefirst and second passages 60, 62 where the carrier gas is rapidly heatedby heating elements 64. Additional or fewer passes can be provided toobtain desired heating of the carrier gas within the packagingconstraints.

The heated carrier gas converges to an outlet 66 where the gas isfocused by a deflecting cone 70. In one example, the deflecting cone 70is constructed from a stainless steel material. The deflecting cone 70prevents the erosion of the ceramic insulating cone 68 over time toreduce the service requirements for the heater assembly 34 and extendits life.

An outlet fitting 72 is received by an end of the heater housing 44 andsecured thereto by a weld bead 74. The outlet fitting 72 includes anindentation 90 that receives a temperature sensor 96 for temperaturefeedback to the control unit 18. The temperature sensor 96 is providednear the outlet 66 for monitoring the temperature of the heater core 42.The temperature sensor 96 is in communication with the control unit 18so that the desired carrier gas temperature can be maintained. In oneexample, the unit 10 can be shut down if no heating of the carrier gasis detected. In another example, the unit 10 can be shut down ifundesirably high temperatures are reached.

Referring to FIGS. 2 and 3 b, bosses 92 on the gun housing 28, whichprovide the locating features 73 for a supplemental insulating cone 75.The front portion of the heater assembly 34 is closely fitted withsupplemental insulating cone 75 and is retained in this position by thebiasing member 48. This way the heater assembly 34 is maintained inproper orientation within the gun housing 28 without the use ofadditional fasteners in the example.

The outlet fitting 72 receives a nozzle 76 that provides a venturi foraccelerating the carrier gas. The outlet fitting 72 includes a hole 94for receiving a set screw (not shown) that secures the nozzle 76 to theoutlet fitting 72. The nozzle 76 includes a throat 78. In one example, aconverging section is provided upstream from the throat 78, and adiverging section is provided downstream from the throat. In oneexample, a powder feed passage 80 is provided in the nozzle 76downstream from the throat 78 for introducing powder material providedthrough a powder feed line 82. A tube 84 is received in an end of thenozzle 76, which deposits the supersonic powder material on thesubstrate.

A shroud 86 is secured to the gun housing 28 and at least partiallysurrounds the tube 84. The shroud 86 prevents the tube 84 from becomingbent or damaged, which would change the powder material depositioncharacteristics. Moreover, the shroud 86 protects the user from unwantedcontact with the tube 84, which could burn the user. Openings 88 areprovided in the shroud 86 to provide cooling to the nozzle 76 and tube84.

A pressure sensor 98 (FIG. 3 a) is in fluid communication with the spraygun 20 to monitor the pressure of the carrier gas. In one example, thepressure sensor 98 is used to ensure that sufficient carrier gaspressure is available to cause adequate flow through the heater core 42to prevent over heating in the event insufficient gas is present.Pressure sensor 98 is located in the space between the inlet fitting 36and the retaining cup 46. In this location the sensitive pressure sensorcircuitry is maintained at a sufficiently cool temperature so as toensure a long service life.

Although example embodiments have been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

1. A cold spray gun comprising: a gun housing; a heater assemblyarranged in the gun housing for heating a carrier gas, the heaterassembly including multiple concentric passages providing a carrier gaspassageway and converging to a common outlet, at least one of thepassages including a heating element, and at least another of thepassages arranged radially outward of the heating element and unheatedfor insulating the gun housing from heat.
 2. The cold spray gunaccording to claim 1, wherein the heater assembly includes a ceramicheater core that provides the multiple concentric passages.
 3. The coldspray gun according to claim 2, wherein the ceramic heater core is aone-piece, unitary structure.
 4. The cold spray gun according to claim3, wherein at least one of the multiple concentric passages are providedby generally concentric, spaced apart walls interconnected by supportlegs, the support legs separating the passage into circumferentialchannels.
 5. The cold spray gun according to claim 2, wherein one end ofthe heater core is received by an aperture of an insulating cone, theinsulating cone providing the common outlet.
 6. The cold spray gunaccording to claim 5, wherein the heater assembly includes a heaterhousing at least partially surrounding the heater core and insulatingcone.
 7. The cold spray gun according to claim 6 comprising asupplemental insulating cone arranged between the heater assembly andthe heater housing, the heater housing comprising a metallic structure.8. The cold spray gun according to claim 7 comprising a nozzle supportedby the heater housing, the nozzle including a venturi for acceleratingthe carrier gas.
 9. The cold spray gun according to claim 8 comprisingan outlet fitting secured to the heater housing, the outlet fittingremovably receiving the nozzle.
 10. The cold spray gun according toclaim 6 comprising a spring biasing member urging the heater core to anend of the heater housing.
 11. The cold spray gun according to claim 5,wherein the insulating cone is non-metallic, and a deflecting cone issupported on an inside of the insulating cone at the common outlet. 12.The cold spray gun according to claim 5, comprising a nozzle removablyreceived by an outlet fitting on the heater assembly for receiving thecarrier gas and powdered material; a tube supported by the nozzle andextending from the gun housing away from the heater assembly forexpelling the intermixed carrier gas and powdered material from the coldspray gun; and a shroud supported on the gun housing and at leastpartially surrounding the tube, the insulating cone arranged between theshroud and the heater assembly.
 13. The cold spray gun according toclaim 12, wherein the nozzle includes a venturi having a throat foraccelerating the carrier gas, the powdered material introduceddownstream from the throat.
 14. The cold spray gun according to claim12, wherein the nozzle is arranged outside of the gun housing and withinthe shroud.
 15. A cold spray gun comprising: a gun housing includingfirst locating features extending interiorly; and a heater assemblyarranged in the gun housing and including second locating featurescooperating with the first locating features for locating the heaterassembly within the gun housing.
 16. The cold spray gun according toclaim 15, wherein the first locating features are provided by bossesextending from the gun housing, the bosses received by indentationsprovided in the heater assembly.
 17. The cold spray gun according toclaim 16, wherein the heater assembly includes an insulating coneproviding the indentations.
 18. The cold spray gun according to claim15, wherein the second locating feature includes a groove provided by aninlet fitting of the heater assembly, the groove receiving a protrusionextending from the gun housing.
 19. A cold spray gun comprising: a gunassembly; a nozzle arranged within the gun assembly and including acarrier gas passageway for receiving a carrier gas and powderedmaterial, the nozzle including a powder feed passageway intersectingwith the carrier gas passageway for introducing the powdered material tothe carrier gas; a carrier gas feed line in fluid communication thecarrier gas passageway within the gun assembly; and an aperture in thecarrier gas passageway arranged upstream from where the carrier gas andpowder feed passageways intersect for leaking carrier gas in acontrolled amount within the gun assembly for pressurizing the gunassembly to prevent infiltration of the powdered material into the gunassembly.
 20. The cold spray gun according to claim 19 comprising aheater assembly including a heating element for heating the carrier gas,the aperture provided in the heater assembly upstream from the heatingelement.
 21. The cold spray gun according to claim 20, wherein the gunassembly includes a gun housing having two halves secured to one anotherabout the heater assembly, the aperture pressurizing the gun housing.22. The cold spray gun according to claim 1, wherein the heater coreincludes the heating element, which is configured to heat the at leastone of the passages to between 400-650° C.
 23. The cold spray gunaccording to claim 4, wherein the heater assembly is arranged fluidlyupstream from where the carrier gas passageway intersects a powder feedpassage.
 24. The cold spray gun according to claim 15, the heaterassembly including includes a heater core that provides multipleconcentric passages providing a carrier gas passageway and converging toa common outlet, at least one of the passages including a heatingelement, and at least another of the passages arranged radially outwardof the heating element and unheated for insulating the gun housing fromheat.
 25. The cold spray gun according to claim 24, comprising a springbiasing member urging the heater core to an end of the heater housing.